Обсуждение: help wanted (fmgr.c)
I am a little stuck of a question. In fmgr.c:1698, function "InputFunctionCall" at line 1718 /* Should get null result if and only if str is NULL */ if (str == NULL) {........ What are we testing to be NULL here? Do we expect str to changed at line 1715 ( result = FunctionCallInvoke(&fcinfo); ) Please advice, Gevik.
At 2006-09-11 10:25:22 +0200, pgdev@xs4all.nl wrote: > > What are we testing to be NULL here? > Do we expect str to changed at line 1715 No. (Read the comment just above the function.) The code is like this, starting from line 1703: if (str == NULL && flinfo->fn_strict) return (Datum) 0; That is, if the function is declared strict, and the argument (str) is 0, just return NULL straightaway. Then it sets up the fcinfo and calls the function, and then: ... /* Should get null result if and only if str is NULL */ if (str == NULL) { if (!fcinfo.isnull) elog(ERROR, "input function %u returned non-NULL", fcinfo.flinfo->fn_oid); } else { if(fcinfo.isnull) elog(ERROR, "input function %u returned NULL", fcinfo.flinfo->fn_oid); } This says: If the argument is NULL and the input function didn't return a NULL, log an error; but if the argument is non-NULL and the function returned NULL, log this other error. (Note that a function would set fcinfo->isnull to indicate that it wants to return an SQL NULL, as explained in $DOC/plhandler.html) -- ams
Thank you for your reply..... I found my bug in the code which made the function behave strangely. On Mon, 2006-09-11 at 14:23 +0530, Abhijit Menon-Sen wrote: > At 2006-09-11 10:25:22 +0200, pgdev@xs4all.nl wrote: > > > > What are we testing to be NULL here? > > Do we expect str to changed at line 1715 > > No. (Read the comment just above the function.) > > The code is like this, starting from line 1703: > > if (str == NULL && flinfo->fn_strict) > return (Datum) 0; > > That is, if the function is declared strict, and the argument (str) is > 0, just return NULL straightaway. Then it sets up the fcinfo and calls > the function, and then: > > ... > > /* Should get null result if and only if str is NULL */ > if (str == NULL) > { > if (!fcinfo.isnull) > elog(ERROR, "input function %u returned non-NULL", > fcinfo.flinfo->fn_oid); > } > else > { > if (fcinfo.isnull) > elog(ERROR, "input function %u returned NULL", > fcinfo.flinfo->fn_oid); > } > > This says: If the argument is NULL and the input function didn't return > a NULL, log an error; but if the argument is non-NULL and the function > returned NULL, log this other error. (Note that a function would set > fcinfo->isnull to indicate that it wants to return an SQL NULL, as > explained in $DOC/plhandler.html) > > -- ams >